User's Manual | ACOM 1010 | HF Linear Amplifier
July 2021
S e c t i o n OPERATION | Page 25 of 40
b)
Tuning Procedure
(1) Once the antenna and band have been selected (and the
TUNE
and
LOAD
adjustments
have been initially set as indicated in
Table 4-1 Approximate tuning preset
), apply between
10 and 20 W of continuous (key down CW) drive signal.
(2) Look at the upper LED bar-graph (FORWARD POWER) and adjust the
TUNE
(right hand)
capacitor for maximum FWD indication.
(3) Watch the three TRI LED indicators above the
LOAD
(left hand) knob and turn it in the
indicated direction to center the green light.
(4) Increase the drive power to get the desired nominal output; then repeat steps (2) and
(3), always peaking output with the
TUNE
adjustment.
No light on the TRI indicator means that the tuning is too far off. To correct this, turn the
LOAD
and
TUNE
knobs around the table-suggested positions until the TRI indicator
illuminates.
Figure 4-1 Using TRI tuning aid
No light:
Use TUNE knob for
max. Power to get any
marker.
Tuning is a far left:
Turn LOAD knob to the
right to get the inside
markers.
Tuning is a far right:
Turn LOAD knob to the
left to get inside
markers.
Marker inside:
Turn LOAD knob slightly
left to
center it.
LOAD is tuned:
Turn TUNE knob to
peak Forward Power.
Figure 4-1 Using TRI tuning aid
The TRI indicator will not illuminate until at least 20 W of forward power (output) is achieved. In the event
successful matching cannot be accomplished, check the
BAND
switch position and antenna selection. Then
check the antenna SWR at the same drive frequency.
c)
Tuning hint
A benefit of TRI is that the knob positions are virtually independent. The plate-load resistance decreases to
the right and increases to the left of the TRI center. A centered tuning indication corresponds to the proper
LOAD
capacitor tuning, which presents an optimum load resistance to the tube.
If the
LOAD
knob is turned to the left with a centered TRI, there will be more gain, but less linearity. When
available drive power is insufficient or when less output but better efficiency is needed, e.g., for RTTY and
SSTV, this may be desirable. Tuning to the right of the center would lead to the opposite result, i.e., less
gain and more power attainable. Of course, this requires more drive power, more plate current, and more
plate heat, which shortens tube's-expected life.